Search

Iron, N-codoped carbon materials (Fe-N-C) are promising electrocatalysts toward oxygen reduction reactions due to their high atom utilization efficiency and intrinsic activity. Nanostructuring of the Fe-N-C materials, such as introducing porosity into the carbon structure, would be conducive to further increasing the exposure of active sites as well as improving the mass transfer. Herein, we explore the potential of iron complex-functionalized micelles of mesoporous SiO

The designability and adjustability of the pore structure are vital advantages of metal–organic framework (MOF) materials for separation. Their exploration in the field of membrane separation is still inadequate, especially for the regulation of the pore environment based on the inorganic secondary building unit (SBU). In this work, we have studied the effect of the pore environment regulated by the SBU on the gas separation performance of MOF membranes for the first time. The Fe3(μ3-O)(CH3COO)6 SBU of the parent framework (soc-MOF, a stable microporous Fe-MOF) was in situ modified with imidazole (IM) molecules to construct the soc-MOF-IM polycrystalline membrane. The exact location of the incorporated IM and the narrowed pore size are observed based on the determined crystal structure. The gas solubility, diffusivity and separation performance of the two membranes are evaluated. Compared to the soc-MOF membrane with a H2/CO2 selectivity of 6, the soc-MOF-IM polycrystalline membrane possesses a significantly enhanced H2/CO2 selectivity (48), which is mainly attributed to the triggered molecular sieving effect. Thanks to the facile introduction of functional molecules and precise adjustment of the pore environment, SBU modification can be a powerful strategy to improve the separation performance of MOF membranes.

Vinylidene fluoride (VDF) is one of the major fluorinated monomers. Currently, it is produced via the pyrolysis of 1-chloro-1,1-difluoroethane at above 650 °C without any catalyst. Herein, we propo...

Dissipative particle dynamics (DPD) simulations were applied to investigate the solution self-assembly and pH-responsive behavior of hydrophobic DCPD (dicyclopentadiene)-loaded microcapsules from triblock copolymers poly (1,2-ethanediol, homopolymer-b-2-Diethylaminoethylmethacrylate-b-methyl methacrylate) (PEG- b -PDMAEMA- b -PMMA). Results indicate that micelles with longer hydrophilic PEG blocks and shorter hydrophobic PMMA blocks were in favor of encapsulating hydrophobic DCPD. Cross-linking at the core/shell interface generates a chemically bonded network structure in the micelle and leads to a significant decrease of their thermodynamic mobility (i.e., the increase of stability). Both non cross-linked and cross-linked micelles show a good pH-responsive behavior. In particular, cross-linked micelles still have the ability to carry DCPD due to the incomplete dispersion even completely protonation of PDMAEMA, which indicates that the cross-linked micelles could be expected to realize the slow release of encapsulated DCPD agent.

N-doped ordered mesoporous carbons (NOMC) were prepared with mixed solution of urea and sucrose as carbon source and nitrogen source. SBA-15 was adopted as the hard template. The effect of urea to sucrose molar ratio on NOMC was investigated. NOMC samples were characterized by techniques such as BET, TEM, XPS and TG. The catalytic performances of NOMC catalysts were evaluated for the pyrolysis of 1-chloro-1,1-difluoroethane (HCFC-142b, CH3CClF2) to vinylidene fluoride (VDF, CH2=CF2). The catalytic reactions were carried out at 400 °C and space velocity of 600 h−1 (based on HCFC-142b). The results indicate that NOMC exhibits a stable activity at 400 °C with high HCFC-142b conversion and selectivity to VDF. The textural parameters of NOMC play a major role in VDF selectivity and N species over the carbon surface are responsible for NOMC catalytic performance. Compared with the temperatures of industrial manufacture of VDF at 650–700 °C, the NOMC catalysts provide a promising pathway to produce VDF at much lower temperatures (below 400 °C).

Uniform, free-standing and cubic SrF2 microparticles were successfully fabricated by a facile hydrothermal method with ethylenediaminetetraacetic acid (EDTA) as the chelating agent. The influences of preparation conditions, such as the pH value, amount of EDTA and hydrothermal time, on the formation of SrF2 crystals were investigated. The formation mechanism of cubic SrF2 particles was proposed based on the experimental results. Following calcination in air at 500 °C, SrF2 particles were evaluated as the catalyst for the pyrolysis of 1-chloro-1,1-difluoroethane (HCFC-142b, CH3CClF2) to vinylidene fluoride (VDF, CH2CF2) at 350 °C and a space velocity of 600 h−1. The results indicate that SrF2 cubes exhibit high catalytic activity with a HCFC-142b conversion of about 70% and a selectivity to VDF of 80–87%. No significant deactivation was observed within the time on stream of 30 h. With the reaction temperature increased to 450 °C, the conversion of HCFC-142b is close to 94%, while the selectivity to VDF remains almost unchanged. Although the SrF2 catalyst prepared by the conventional precipitation method also shows high conversion, its selectivity to VDF is only around 50–70%. We suggest that the surface acidity and specific surface area play major roles in the catalytic performance. Compared with the temperatures for industrial manufacture of VDF of 650–700 °C, the SrF2 catalysts provide a promising pathway to produce VDF at much lower temperatures.

Cross-linking with large flexible molecules is a common method to improve the stability and control the interlayer spacing of graphene oxide (GO) membranes, but it still suffers from the limitation of low water flux. Herein, a novel high flux GO membrane was fabricated using a pressure-assisted filtration method, which involved a synergistic chemical cross-linking of divalent magnesium ions and 1,6-hexanediamine (HDA) on a polyethersulfone (PES) support. The membrane cross-linked with magnesium ions and HDA (GOHDA–Mg2+) exhibited a high water flux up to 144 L m−2 h−1 bar−1, about 7 times more than that of cross-linked GO membranes without adding magnesium ions (GOHDA), while keeping excellent rejection performance. The GOHDA–Mg2+ membrane also showed an outstanding stability in water for a long time. The effects of magnesium ions on the GOHDA–Mg2+ membrane were analyzed using several characterization methods, including Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results indicated that magnesium ions not only promoted reasonable cross-linking, but also improved the stacking of GO sheets to give lower mass transfer resistance channels for water transport in the membranes, resulting in the ultrahigh permeance of the GO membranes.

Hydrophobic oil additives have been shown to be a unique class of chemicals in solution, which affect the stability of foam films. While the oil-induced destruction of a foam film has been largely ...

This study uses an all-atom computational model to investigate the temperature dependent heterogeneity and percolation in a nanofilm system of short linear epoxy chains on a solid graphene surface. The heterogeneity, which indicates having physical characters that vary within the nanofilm, is mainly manifested in distributions of volume, energy and the dynamic properties. Local glass transition temperatures, Tgs, from above properties depend largely on the separation to the graphene surface, and the glass transition of the nanofilm is asynchronous along the film normal. Distinct Tg increases and decreases are particularly observed in the solid and free interfaces, respectively, compared with the bulk. From the dynamic heterogeneity, percolation effect, which indicates the connectivity of mobile and immobile domains, of the nanofilm is also observed during glass transition by plotting internal atomic mobility distribution diagrams. A multi-stage percolation mechanism based on the glass transition state and the connection state of immobile and mobile domains of the nanofilm is developed. A relatively immobile domain near the graphene surface is observed, even at temperatures much higher than Tg, and it initiates the dynamic percolation. The interconnection of immobile domains after percolation accelerate the transition from the rubbery to the glassy state.

Dissipative particle dynamics (DPD) simulation is used to study the effect of pH on the morphological transition in micelles assembled from dirhamnolipids (diRLs), and analyze the pH-driven mechanism and influence factors of micellar surface patterns. At pH4.0, various multilayer structures with homogeneous surface patterns are observed, whereas diRLs can self-assemble into novel anisotropic morphologies with phase-separated surface patterns at pH7.4, such as patchy spherical micelles, rod-like micelles with helical surface patterns and a lamellar phase with anisotropic surface patterns. The change in a surface pattern results from the diverse molecular arrangement in the course of assembly due to the deprotonation of carboxyl groups. Further studies show that influence factors, such as molecular structure, solvent selectivity and intramolecular interaction, are closely associated with the changes in surface patterns and topological structures. In detail, decreasing the critical packing parameter of rhamnolipids, increasing the solution polarity and weakening the compatibility between rhamnose rings and alkyl chains are all beneficial to the formation of phase-separated surface patterns. Remarkably, a wider variety of surface patterns (randomly anisotropic surface patterns) can be further obtained with the different factors mentioned above. This work is expected to extend the applications of diRLs to advanced functional materials like drug delivery, optoelectronics and nanofiltration membranes.

Graphene oxide (GO) lamellar membranes exhibit great potential for application in molecular separation. However, they are still limited by low water permeation and swelling effects. Here, we develop robust K+-crosslinked reduced GO (rGO–K+) membranes for treating wastewater containing multivalent heavy metal ions. The rGO–K+ membranes demonstrated a water permeance of 86.1 L m−2h−1 bar−1 and a rejection rate of 99.8% for FeCl3, which exceed the corresponding values of state-of-the-art nanofiltration (NF) membranes for multivalent metal ion rejection. Further, the rGO–K+ membranes exhibited excellent aqueous stability under a high pressure (up to 9 bar) and acidic, neutral, and alkaline conditions. The improved permeability of the rGO–K+ membranes was attributed to the cation–π interactions between K+ and the rGO sheets, which fixed and enlarged the interlayer spacing, as well as increased the surface hydrophilicity, thus weakening the water transport resistance. The intercalated K+ linked the adjacent layers through the cation–π interactions, which enhanced the membrane stability. The prepared rGO–K+ membranes have potential for use in membrane separation in industrial applications.

Density functional theory calculation was conducted to investigate the adsorption behavior and mechanism of benzotriazole (BTA) on the copper surface with the defects of vacancy, impurity, and grain boundary (GB). On the Cu (111) surface with vacancies, BTA tends to obliquely, rather than vertically, adsorb on the copper surface. The surface doped with Zn and O has stronger adsorption activity for negatively charged particles compared with the surface doped with Ni and S. For impurity and GB surface, the adsorption energy and transferred charge show that the oblique and horizontal adsorption configurations are more stable than the vertical adsorption of BTA. Our findings provide profound explanation for corrosion inhibitor protection of defective metal surface.

Molecular dynamics (MD) simulations were implemented to investigate the effect of single adatom (SA) and Stone-Wales (SW) defects on the longitudinal elastic properties of unidirectional carbon nanotube (CNT)/polypropylene (PP) composites. The longitudinal Young's moduli of individual CNTs and CNT/PP composites were calculated from uniaxial tension simulations, and the interfacial shear strengths (IFSSs) between CNTs and PP matrix were also extracted. The moduli of SA and SW defected CNT/PP composites decrease with the increase of the defect degree, and SW defects have a greater impact on the moduli than SA defects. Moreover, the intrinsic moduli of the CNTs with SA and SW defects also decrease due to the structural relaxations under tension loading as the defect degree increases. However, the IFSSs of SA and SW defected CNT/PP composites tardily decrease and increase with the increase of the defect degree, respectively. Analysis of the parametric loss ratios indicates that the longitudinal elastic properties of SA and SW defected CNT/PP composites strongly depend on that of the CNTs, and the variation of interfacial bonding characteristics caused by SA and SW defects might have a negligible effect.

γ-Al 2 O 3 with 3/4 sphere and cabbage-like structures were prepared via hydrothermal synthesis. Then they were evaluated as catalysts for the dismutation of HCFC-22 as a model reaction for Cl/F exchange reactions and compared with a commercial γ-Al 2 O 3 . The results indicate that both hydrothermal samples are formed by the loose assembly of nano-sheets. For cabbage-like alumina, hollow structure is detected. Aluminum chlorofluoride (ACF) structure with strong Lewis acidity is beneficial for dismutation of HCFC-22. Following pre-fluorination by HCFC-22, the high activity of cabbage-like γ-Al 2 O 3 is attributed to the high content of ACF. It indicates that cabbage-like structure tends to form more ACF structure.

Dissipative particle dynamics (DPD) simulations were applied to investigate the coating repair agent dicyclopentadience (DCPD) in pH-sensitive micelles. The results show micelles self-assembled from triblock copolymers with strong hydrophobic interaction are not conducive to loading DCPD, and only micelles with weak interaction parameter can encapsulate DCPD well. After protonation, the structure of micelle was disassembled and DCPD beads have a stronger ability to shrink polymer chains and exposed to water. This work provides mesoscopic insight into self-assembly and disassembly of desired agent-loaded micelle, and might be useful for the design of new materials for agent delivery.

Molecular dynamics simulations are used to investigate the effect of graphene dispersion on the equilibrium structure and deformation of graphene/eicosane composites. Two graphene sheets with four different interlayer distances are incorporated, respectively, into a eicosane matrix to form graphene/eicosane composites representing different graphene dispersions. With greater graphene dispersion, the “adsorption solidification” of the eicosane increases, where eicosane molecular lamination, orientation, and extension become more uniform and stronger. In addition, eicosane molecular motion is inhibited more in the direction perpendicular to graphene surfaces. When these graphene/eicosane composites are deformed, the free volume initially increases slowly due to small, scattered voids. After reaching the yield strains, the free volume rises sharply as the structures of composites are damaged, and small voids merge into large voids. The damage always occurs in the region of the composite with the weakest “adsorption solidification.” Since this effect is stronger when the graphene sheets are more dispersed, more complete dispersion results in higher composite yield stresses. Lessons from these simulations may provide some insights into graphene/polyethylene composites, where suitable models would require very long equilibration times.

Hydrofluorocarbons (HFCs) which are usually potent greenhouse gases are regulated by the Montreal Protocol and its amendments, especially the recent Kigali Amendment. Dehydrofluorination of HFCs is an efficient route for the conversion of these greenhouse gases to value added and environmentally benign chemicals. Although AlF3 with strong Lewis acidity catalyzes dehydrofluorination, it also favors carbon deposition. MgF2 with weak acidity inhibits coking significantly. Unfortunately, MgF2 sinters dramatically at temperatures below 300 °C leading to the low activity for dehydrofluorination. In the present work, we report that sub-nano MgF2 embedded in carbon fibers and electrospun MgF2 fibers prevent sintering of MgF2 during dehydrofluorination reaction. Via simple and one-step electrospinning and calcination in a N2 (for embedded MgF2) or air (for MgF2 fibers) atmosphere, embedded MgF2 with particle sizes between 3–6 nm and pure MgF2 fibers with diameters of around 100 nm were fabricated. No sintering was observed following reaction at 450 °C. The fine MgF2 particles and MgF2 fibers facilitate the formation of under coordinated Mg species in MgF2 which are the weak acid sites. By embedding MgF2 or fabrication of MgF2 fibers, weak acid sites are increased significantly, while strong acid sites remain almost unchanged. Hence, they show significantly higher reaction rates than MgF2 prepared by precipitation of Mg(CH3COO)2·4H2O with NH4F for the dehydrofluorination of 1,1,1-trifluoroethane (HFC-143a) to VDF (CH2CF2) at 450 °C.

Self-assembly of asymmetric block copolymers (BCPs) around active pore edges has emerged as an important strategy to produce smart membranes with tunable pathways for solute transport. However, thus far, it is still challenging to manipulate pore shape and functionality for directional transformation under external stimuli. Here, a versatile strategy by mesoscale simulations to design stimuli-responsive pores with various edge decorations in hybrid membranes is reported. Dopant BCPs are used as decorators to stabilize pore edges and extend their function in reconfiguring pores in response to repeated membrane stretching/shrinking caused by external stimuli. The decoration morphologies are predictable since the assemblies of dopant BCPs around pore edges are closely related to their self-assemblies in solution. The coassembly between different BCPs in the hybrid membrane for the control of pore morphology is featured, and the parameter settings, including block incompatibility and molecular architecture for the construction of a specific pore, are determined. Results show that harnessed dopant BCPs in the hybrid membrane can enhance pore formation and induce directional pore shape and functionality transformation. Diversified pore decorations exhibit potential that can be further explored in selective solute transport and the design of stimuli-responsive smart nanodevices.

Carbon nanotubes (CNTs) are extensively adopted in the applications of biotechnology and biomedicine. Their interactions with cell membranes are of great importance for understanding the toxicity of CNTs and the application of drug delivery. In this paper, we use atomic molecular dynamics simulations to study the permeation and orientation of pristine and functionalized CNTs in a lipid bilayer. Pristine CNT (PCNT) can readily permeate into the membrane and reside in the hydrophobic region without specific orientation. The insertion of PCNTs into the lipid bilayer is robust and independent on the lengths of PCNTs. Due to the presence of hydroxyl groups on both ends of the functionalized CNT (FCNT), FCNT prefers to stand upright in the lipid bilayer center. Compared with PCNT, FCNT is more suitable to be a bridge connecting the inner and outer lipid membrane. The inserted CNTs have no distinct effects on membrane structure. However, they may block the ion channels. In addition, preliminary explorations on the transport properties of CNTs show that the small hydrophobic molecule carbon dioxide can enter both PCNT and FCNT hollow channels. However, hydrophilic molecule urea is prone to penetrate the PCNT but finds it difficult to enter the FCNT. These results may provide new insights into the internalization of CNT in the lipid membrane and the transport properties of CNTs when embedded therein.

Nano-Cr2O3 was prepared via solution combustion synthesis (SCS) with Cr(NO3)3·9H2O as the Cr precursor and glycine as the fuel. The effect of molar ratio of glycine to Cr in the feed during solution combustion was investigated. Cr2O3 samples were characterized by XRD, SEM, TEM, H2-TPR, and XPS. In addition, these catalysts were evaluated for the dehydrofluorination of 1,1-difluoroethane producing vinyl fluoride (VF, CH2=CHF). The results confirm that Cr2O3 is in relatively uniform flakes or flat particles via solution combustion synthesis with the particle size of 50–200 nm and composed by the aggregation of 58–77 nm nanoparticles. The specific surface area of higher than 30 m2 g−1 is achieved, which is comparable to the values obtained by solvothermal route. For the dehydrofluorination of 1,1-difluoroethane, high conversion levels (83 % for commercial catalyst and 93 % for SCS catalyst) are achieved at 350 °C, and the activity of SCS catalyst is at least 2× higher than that of commercial Cr2O3 at reaction temperatures below 300 °C. Compared with commercial Cr2O3, XPS, and H2-TPR reveal the higher CrO3 contents on the surface of Cr2O3 derived from SCS. It is suggested that CrO3 plays a major role in the catalytic performance as high-valent Cr species such as Cr(VI) are vital for the reaction because they could be transformed to the active species such as CrO x F y . In addition to the high activity, compared with commercial Cr2O3, SCS catalyst also show higher stability. Following the reaction of 120 h at 300 °C, no noticeable deactivation is observed while the activity of commercial Cr2O3 declines with TOS. High surface area and much smaller size of Cr2O3 crystalline favors the formation of CrO x F y during reaction over Cr2O3-3.33 catalyst probably contribute to the high activity and stability.

Atomistic molecular dynamics simulations have been performed to explore the effect of interfacial bonding on the interphase properties of a nanocomposite system that consists of a silica nanoparticle and the highly cross-linked epoxy matrix. For the structural properties, results show that interfacial covalent bonding can broaden the interphase region by increasing the radial effect range of fluctuated mass density and oriented chains, as well as strengthen the interphase region by improving the thermal stability of interfacial van der Waals excluded volume and reducing the proportion of cis conformers of epoxy segments. The improved thermal stability of the interphase region in the covalently bonded model results in an increase of ∼21 K in the glass transition temperature (Tg) compared to that of the pure epoxy. It is also found that interfacial covalent bonding mainly restricts the volume thermal expansion of the model at temperatures near or larger than Tg. Furthermore, investigations from mean-square displacement and fraction of immobile atoms point out that interfacial covalent and noncovalent bonding induces lower and higher mobility of interphase atoms than that of the pure epoxy, respectively. The obtained critical interfacial bonding ratio when the interphase and matrix atoms have the same mobility is 5.8%. These results demonstrate that the glass transitions of the interphase and matrix will be asynchronous when the interfacial bonding ratio is not 5.8%. Specifically, the interphase region will trigger the glass transition of the matrix when the ratio is larger than 5.8%, whereas it restrains the glass transition of the matrix when the ratio is smaller than 5.8%.

Molecular dynamics simulations were carried out to investigate the influence of cations (Ca2+/Mg2+) on the stability of the foam system stabilized by sodium dodecyl polyoxyethylene sulfonate (A12E2SO3). First, the structure of A12E2SO3 monolayer at the air/water interface was studied through analyzing the distribution of A12E2SO3 headgroups and the orientation of surfactant molecules. Results show that the addition of Mg2+ can increase the distance between A12E2SO3 headgroups, broaden the distribution thickness of A12E2SO3 headgroups along z axis, and improve the orientation of A12E2SO3 molecules, which favored the foam stability. On the contrary, the addition of Ca2+ in the foam system made surfactant molecules more aggregated, which was detrimental to the foam stability. Second, the interaction of surfactant molecules and cations was also studied through calculating their binding/dissociation energy and mobility. Results reveal that the binding tendency of the head-Ca2+ ion-pair was stronger than that of the head-Mg2+ ion-pair, which disturbed the foam stability. Third, we studied the hydration of surfactant headgroups and cations through calculating the number and the mobility of hydrated water molecules around headgroups. Results show that due to the extra hydration of cations in the foam system, especially for that with the addition of Mg2+, the number of water molecules around headgroups was increased and their mobility was restricted, which was beneficial to the foam stability. In addition, two forms of hydrogen bond bridging structures (O1⋯H2O⋯O2 and O2⋯H2O⋯Os) were observed for the first time in anionic surfactants. The location and the formation probability of these structures were found to be related to the gauche conformation of A12E2SO3 headgroup backbones. It was also found that hydrogen bond bridging structures can affect the foam stability.

Most of existing nanocontainers suffer from tedious, complicated and unsustainable assembly process which restricts their application in corrosion protection as smart inhibitor carriers. In this study, we adopted the framework-hybridization approach to prepare a smart anticorrosion system (MBT@Ph-HPMO), with MBT inhibitor as cargo and phenylene-bridged hollow periodic mesoporous organosilica (Ph-HPMO) as nanocontainer. Results reveal that the π-π stacking between MBT and framework of Ph-HPMO serves as nature valve, which is supplemented by the molecular dynamic simulation. The encapsulated inhibitor was loaded into Ph-HPMO at neutral pH, demonstrating fast release in acidic environment. On-demand release of inhibitors from MBT@Ph-HPMO contributed to achieving in situ active corrosion protection. Anticorrosion performance of MBT@Ph-HPMO for copper alloy was evaluated in 3.5 wt% NaCl solution for a period of 30 days. The alloy exhibited the slightest corrosion damage in the corrosion medium with the addition of 0.24 wt% MBT@Ph-HPMO. This facile and versatile strategy will have broad applications in new class of nanocontainers fabrication and open up a new prospect for active corrosion protection.

Water permeation through stacked graphene oxide (GO) membranes is a key for its promising potential for filtration and purification applications. The permeation in GO membranes prepared with different physical and chemical structures (GO flakes) varies significantly, which requires to be elucidated. Here, we fabricated four types of GO flakes with different physical and chemical structure by modified Hummers method with controlling of temperature. The results showed a sensitive temperature dependence of the size and oxygen content of the GO flakes. The flake size is negatively correlated with water flux and has a far higher effect on permeation compared with that of the oxygen content. The GO membrane made of the smallest flakes exhibits ultrahigh water flux of up to ~53.7 L m−2 h−1 bar−1, which is more than three times that of conventional large GO membranes, while still maintaining a high rejection rate of ~95.7% for pararosaniline. Importantly, of all pristine GO membranes without any chemical modifications, this is the most permeable membrane for dyes. Our study reveals a sensitive effect of the physical and chemical structures of GO on water permeation and represents a facile step regarding ultrahigh flux GO membranes for water purification.

Ultrafiltration (UF) membranes have found great application in sewage purification and desalination due to their high permeation flux and high rejection rate for contaminants under low-pressure conditions, but the flux and antifouling ability of UF membranes needs to be improved. Tetrakis (4-carboxyphenyl) porphyrin (TCPP) has good hydrophilicity, and it is protonated under strongly acidic conditions and then forms strong hydrogen bonds with N, O and S, so that the TCPP would be well anchored in the membrane. In this work, NaHCO3 was used to dissolve TCPP and TMC (trimesoyl chloride) was used to produce a strong acid. Then, TCPP was modified in a membrane with a different rejection rate by a method similar to interfacial polymerization. Performance tests of TCPP/polysulfone (PSf) membranes show that for the membrane with a high BSA (bovine serum albumin) rejection, when the ratio of NaHCO3 to TCPP is 16:1 (wt.%), the pure water flux of membrane Z1 16:1 is increased by 34% (from 455 to 614 Lm&minus, 2h&minus, 1bar&minus, 1) while the membrane retention was maintained above 95%. As for the membrane with a low BSA rejection, when the ratio of NaHCO3 to TCPP was 32:1, the rejection of membrane B2 32:1 was found to increase from 81% to 96%. Although the flux of membrane B2 32:1 decreased, it remained at 638 Lm&minus, 1, which is comparable to the reported polymer ultrafiltration membrane. The above dual results are thought to be attributed to the synergistic effect of protonated TCPP and NaHCO3, where the former increases membrane flux and the latter increases the membrane rejection rate. This work provides a way for the application of porphyrin and porphyrin framework materials in membrane separation.

SrF2 promotes the dehydrochlorination (DeHCl) of 1,1-difluoro-1-chloroethane, which is the key process for the manufacture of VDF (vinylidene fluoride), one of the most typical fluorinated monomers. However, the selectivity is low as dehydrofluorination (DeHF) to VCF (vinylidene chlorofluoride) competes with the formation of VDF. In this study, SrF2@C (SrF2 embedded in carbon) and SrF2@NC (N-doped carbon) catalysts were fabricated following calcination in N2 with SrC2O4, PVDF (poly vinylidene fluoride) and urea as the precursors. The catalysts were characterized by XRD, SEM, TEM, and XPS. The results show that both the calcination temperature and N-doping play an important role in the conversion of HCFC-142b and the selectivity to VDF and VCF. Calcination at elevated temperatures enhances the Sr-C interaction. For SrF2@C, improved interaction facilitates withdrawing electrons from Sr by the carbon support. By contrast, the strong interaction of Sr with N-doped carbon supply electrons from N species to Sr. The electron deficiency of Sr is favorable for the adsorption of F with higher electronegativity and consequently, DeHF reaction forming VCF. The supply of electrons to Sr by the support improves the formation of VDF (DeHCl). The present work provides a potential strategy for the improvement of selectivity to the target product.

The ocean is rich in medical resources, mineral resources and marine living resources [1], it can for the future development of human society to provide endless valuable wealth and development prospects [2]. In order to facilitate the research on ocean, human designed a large number of underwater vehicles. According to different structures, these submersible can be divided into AUV, ROV or glider. Though their scope of work basically covered the whole underwater world, they still produced the blanks of the operation mode from the seabed to the seabed [3] [4]. So we designed a type of underwater vehicle——autonomous underwater helicopter (AUH) with dished fluid shape to fill the gap. AUH, one kind of AUV, is able to rise or sink, move forward or back, and rotate in place, and the major working model is that it moves from seabed to seabed. Based on the motion characteristics and working mode of the submarine, combined with the submarine observation network, we can use the submarine for continuous submarine exploration and investigation.

Multigeometry nanoparticles with high complexity in composition and structure have attracted significant attention for enhanced functionality. We assess a simple but versatile strategy to construct hybrid nanoparticles with subdivided geometries through the cooperative assembly of diblock copolymer blends with asymmetric architectures. We report the formation of multicompartmental, vesicular, cylindrical, and spherical structures from pure AB systems. Then, we explore the assemblies of binary AB/AC blends, where the two incompatible, hydrophobic diblock copolymers subdivide into self-assembled local geometries, and the complexity of the obtained morphologies increases. We expand the strategy to ternary AB/AC/AD systems by tuning the effect of phase separation of different hydrophobic domains on the surface or internal region of the nanoparticle. The kinetic control of the coassembly in the initial stage is crucial for controlling the final morphology. The interactions of copolymers with different block lengths and chemistries enable the stabilization of interfaces, rims and ends of subdomains in the hybrid multigeometry nanoparticles. With further exploration of size and shape, the dependence of local geometry on the volume fraction is discussed. We show an efficient approach for controllable multigeometry nanoparticle construction that will be useful for multifunctional and hierarchical nanomaterials.

Multicompartment nanostructures, such as microcapsules with clearly separated shell and core, are not easily accessible by conventional block copolymer self-assembly. We assess a versatile computational strategy through cooperative assembly of diblock copolymer blends to generate spherical and cylindrical compartmentalized micelles with intricate structures and morphologies. The co-assembly strategy combines the advantages of polymer blending and incompatibility-induced phase separation. Following this strategy, various nanoassemblies of pure AB, binary AB/AC and ternary AB/AC/AD systems such as compartmentalized micelles with sponge-like, Janus, capsule-like and onion-like morphologies can be obtained. The formation and structural adjustment of microcapsule micelles, in which the shell or core can be occupied by either pure or mixed diblock copolymers, were explored. The mechanism involving the separation of shell and core copolymers is attributed to the stretching force differences of copolymers which drive the arrangement of different copolymers in a pathway to minimize the total interfacial energy. Moreover, by adjusting block interactions, an efficient approach is exhibited for regulating the shell or core composition and morphology in microcapsule micelles, such as the transition from the "pure shell/mixed core" morphology to the "mixed shell/pure core" morphology in the AB/AC/AD micelle. This mesoscale simulation study identifies the key factors governing co-assembly of diblock copolymer blends and provides bottom-up insights towards the design and optimization of new multicompartment micelles.

© 2017 American Chemical Society. Using dissipative particle dynamics simulation, we probe the tunable permeability of cross-linked microcapsules made from pH-sensitive diblock copolymers poly(ethylene oxide)-b-poly(N,N-diethylamino-2-ethyl methacrylate) (PEO-b-PDEAEMA). We first examine the self-assembly of non-cross-linked microcapsules and their pH-responsive collapse and then explore the effects of cross-linking and block interaction on the swelling or deswelling of cross-linked microcapsules. Our results reveal a preferential loading of hydrophobic dicyclopentadiene (DCPD) molecules in PEO-b-PDEAEMA copolymers. Upon reduction of pH, non-cross-linked microcapsules fully decompose into small wormlike clusters as a result of large self-repulsions of protonated copolymers. With increasing degree of cross-linking, the morphology of the microcapsule becomes more stable to pH change. The highly cross-linked microcapsule shell undergoes significant local polymer rearrangement in acidic solution, which eliminates the amphiphilicility and therefore enlarges the permeability of the shell. The responsive cross-linked shell experiences a disperse-to-buckle configurational transition upon reduction of pH, which is effective for the steady or pulsatile regulation of shell permeability. The swelling rate of the cross-linked shell is dependent on both electrostatic and nonelectrostatic interactions between the pH-sensitive groups as well as the other groups. Our study highlights the combination of cross-linking structure and block interactions in stabilizing microcapsules and tuning their selective permeability.

Dissipative particle dynamics (DPD) simulation has been used to study the effect of pH on the morphology transition of micelles assembled by monorhamnolipids (monoRLs). Results show that micellar structures and transition modes with increasing mass concentrations are multiform due to the changeable hydrophilicity of pH-responsive beads at different pH levels. Various chaotic multilayer aggregations of monoRLs are observed at low pH (pH4.0) whereas well-ordered single-layer structures are obtained at high pH (pH7.4). At medium pH region (4.0pH7.4), morphologies with semi-chaotic structures will transform from multilayer to single layer with increasing pH due to the hydrophilicity increase of micelles. In addition, three micellar transition modes are built by varying the hydrophilicity of pH-responsive beads and validated by solvent accessible surface areas (SASAs) as a function of mass concentrations. This work is expected to trigger further studies on the stimuli-driven phenomena of glycolipids.

Multi-geometry nanostructures with high-order, complex, and controllable geometries have attracted extensive attention in the development of functional nanomaterials. A simple and versatile strategy is proposed to construct various anisotropic nanostructures through the directed self-assembly (DSA) of patchy microgels. A general criterion for interaction parameters is developed by the variance analysis method to achieve the formation of 1D nanorods by the single directional DSA process, and 2D or 3D polymorphs including V/T/h/cross shapes, multiple arms, multi-directional bending, single/multiple rings, nanocages, etc., by the multi-directional DSA process of binary microgel blends. At the optimum interaction parameters, the nanorods exhibit the quickest formation process and the most thermodynamically stable geometry, while the various 2D or 3D assemblies exhibit controlled jointing behaviors for versatile assembly geometries. The number of recognition sites on the patchy microgel surface guides the aggregation modes of microgels during the DSA process. These assemblies can bear large curvature variance with the increase of shear rates due to the high flexibility and the ability of adjusting orientation spontaneously. The DSA behavior of patchy microgels differs from the traditional self-assembly process of block copolymers, which may open a new route for guiding the formation of controllable nanoparticle architectures.

Oil phase has strong hydrophobicity and weak interface tension in the foam system, which will destroy the internal structure of foam and reduce the intrinsic stability of the foam film. Coarse-grained molecular simulation techniques were employed to investigate the effect of oil phases on the structural instabilities of two typical foam systems, i.e., ionic sodium dodecyl sulfate (SDS) and nonionic pentaethylene glycol monododecyl ether (C 12 E 5 ). In both systems, the pseudo-emulsion film ruptures at a critical thickness, subsequently the oil phase enters the air-water interface subsequently. Instability mechanisms are obtained by analyzing dynamic processes of the foam systems. For the SDS foam system, an oil-bridge is formed in the foam film, which is attributed to the electrostatic repulsion between the SDS at the oil-water interface and that at the air-water interface, as well as the discontinuous distribution of SDS at the air-water interface caused by the structural reversal of SDS molecules. However, for the C 12 E 5 foam system, oil phase spreads at the air-water interfaces, which is caused by the continuous distribution of the C 12 E 5 molecules at the air-water interface and the attractive interaction between the neutral C 12 E 5 molecules at the air-water interface and that at the oil-water interface. The outcomes of this work shed light on the destructive mechanism of foam films induced by oil phase and provide guidelines for the design of novel oil-resistant foam system.